What Size Nut Do I Need ?

[SimonP85]

The nut and handle for the handle on a ball valve were pretty corroded so I've purchased a new stainless handle to fit. The old nut wouldn't budge so I used a nut spliter to remove it. However, now I'm struggling to struggling to find the correct nut! (Yes probably should have left it how it was!)

M8 no fit
M10 vaguely engages with the thread but is loose and on any tightening just pops off
3/8-16 UNC - Fits perhaps a half turn but no further

This is a 3/4" ISIS ball valve on a 1990 Moody 346 if that helps.

 

[Norman_E]

May well be 3/8 inch BSF which is 20TPI.

 

[Poignard]

The nut and handle for the handle on a ball valve were pretty corroded so I've purchased a new stainless handle to fit. The old nut wouldn't budge so I used a nut spliter to remove it. However, now I'm struggling to struggling to find the correct nut! (Yes probably should have left it how it was!)

M8 no fit
M10 vaguely engages with the thread but is loose and on any tightening just pops off
3/8-16 UNC - Fits perhaps a half turn but no further

This is a 3/4" ISIS ball valve on a 1990 Moody 346 if that helps.

View attachment 93492

If you can measure the threads per inch (or the thread pitch) and the outside diameter of the thread we would be able to tell you what it is likely to be. If you still have the broken nut you can easily measure the TP or pitch without having to crawl in the bilge.

 

[SimonP85]

Thanks for the replies. The pitch is certainly closer to 1mm than 2mm which would support Norman_E's suggestion of BSF and 20TPI. I don't have a vernier calliper so I'll get hold of a 3/8 BSF and keep my fingers crossed!

 

[Boater Sam]

If you are really stuck, pound the M10 nut flat on an anvil or vice with a hammer till it spreads a bit, it may then fit and tighten.

 

[RichardS]

May well be 3/8 inch BSF which is 20TPI.

M10 fine would be very close to 20 TPI so 3/8 BSF sounds right.

Richard

 

[RichardS]

If you are really stuck, pound the M10 nut flat on an anvil or vice with a hammer till it spreads a bit, it may then fit and tighten.

I've never tried that.

It seems a bit counter-intuitive as heating the nut would have the opposite effect and I'd be worried that the TPI would change/distort at the outer edges so the nut would no longer screw on?

Richard

 

[Forty_Two]

The nut and handle for the handle on a ball valve were pretty corroded so I've purchased a new stainless handle to fit. The old nut wouldn't budge so I used a nut spliter to remove it. However, now I'm struggling to struggling to find the correct nut! (Yes probably should have left it how it was!)

M8 no fit
M10 vaguely engages with the thread but is loose and on any tightening just pops off
3/8-16 UNC - Fits perhaps a half turn but no further

This is a 3/4" ISIS ball valve on a 1990 Moody 346 if that helps.

View attachment 93492

Where did you buy the stainless handle?
Thanks

 

[[159032]]

If you are really stuck, pound the M10 nut flat on an anvil or vice with a hammer till it spreads a bit, it may then fit and tighten.

Sounds a bit 'bush mechanic'.

 

[Robin]

Ihad that when we lived in USA and a very kind forumite sent me some spare valves after replacing all, prior to going transat, on his boat, swapped nuts and bingo.

 

[Topcat47]

More likely to be a UNF or BSF thread in that case. Get hold of a set of Zeus Tables from Amazon and a micrometer or vernier. Measure the diameter of the bolt and compare the thread count with the Zeus tables to find the correct nut. As no-one uses these old thread forms other than the Yanks (even they are migrating to metric by default these days) you'll struggle to find something even in the UK (try Classic Marine). Thank the Gods you're not trying to restore a pre-'50's motorbike with WW, Cycle and BSF threads.

 

[tudorsailor]

More likely to be a UNF or BSF thread in that case. Get hold of a set of Zeus Tables from Amazon and a micrometer or vernier. Measure the diameter of the bolt and compare the thread count with the Zeus tables to find the correct nut. As no-one uses these old thread forms other than the Yanks (even they are migrating to metric by default these days) you'll struggle to find something even in the UK (try Classic Marine). Thank the Gods you're not trying to restore a pre-'50's motorbike with WW, Cycle and BSF threads.

Once you have worked out what the thread is, try these guys Contact Us - Group Components They have a warehouse that is an Aladin's cave of odd nuts and bolts.

TS